Users of vacuum-type interrupters do not attach any fixed potential, or any circuit connections to the condensing shield of a vacuum-type circuit interrupter. Instead, they allow the condensing shield to electrically "float," i.e., assume a potential that is dependent upon its capacitance, the unpredictable low surface leakage of the insulators, or casing separating it from the other electrodes or contacts, and electrons and/or ions which strike it. Because of the erratic nature of these effects, a definite potential on the condensing shield is not always possible.